1. Field of the Invention
The present invention relates to a hard disk drive (HDD), and more particularly, to a method of screening an HDD having the possibility of head degradation during an HDD process.
2. Description of the Related Art
A hard disk drive (HDD) is a device that reads and/or writes data from and/or to a disk using a magnetic head. The disk is rotatably mounted on a spindle motor, and information is accessed by the magnetic head, namely, read/write head, mounted on an actuator arm that is rotated by a voice coil motor. The voice coil motor is excited by a current to rotate an actuator and move the read/write head. The read/write head detects a magnetic change occurring on a surface of the disk and reads the information recorded on the surface of the disk. To write information on a data track, current is supplied to the read/write head. The current creates a magnetic field, thereby magnetizing the surface of the disk.
As capacity of an HDD has increased recently, the size of a read/write sensor of a magnetic head has been reduced, and flying height (FH) has also been reduced. Such design of the HDD results in an increase in the possibility of head degradation during an HDD operation. The head degradation directly affects the reliability of the HDD.
After the HDD is assembled, a process of verifying and optimizing various parameters is performed. The process is referred to as the HDD process.
The head degradation is judged in a specific operation of a procedure for verifying the HDD. For example, instability of the magnetic head is checked in an adaptive read channel optimizing (ARCO) operation, which is performed in an early stage of the procedure.
In the conventional art, the instability of the magnetic head is checked using a thermal asperity detection (TAD) function or by examining changes of read parameters in the ARCO operation after a writing operation.
But since the head degradation may occur in any operation during the HDD process due to electrical and/or mechanical stress, the possibility of head degradation may not be determined using only the verification in the specific operation, when a final step of the HDD process finishes.
Particularly, when HDD sets, which have marginally passed process criteria even though performances of their heads have been changed during the HDD process, are put on the market, there is always the possibility of a poorly functioning HDD.
But with the conventional art, it is hard to detect the HDD with the possibility of head degradation in advance, for example, during the HDD process, thereby making it difficult to prevent a poorly functioning HDD.